Molded switch head



L: w. HIGGINS ETAL. 2,820,123

MOLDED SWITCH HEAD 3 Sheets-Sheet 1 A I V \w i Jan. 14, 1958 Filed May18, 1956,

Jan. 14, 1958 L. w. HIGGINS ETAL 2,820,123

, MOLDED [SWITCH HEAD I Filed May 18, 1956 s Sheets-Shae z INVENTORS.Jay/y 4. #5001741! passe. 5 0411/5 4 I r I y Laws way/saws United StatesPatent MOLDED SWITCH HEAD Louis W. Higgins and Russell S. Davis,Detroit, and John A. Herrmanu, Grosse Pointe, Mich., assignors toBullDog Electric Products Company, Detroit, Mich., a corporation of WestVirginia Application May 18, 1956, Serial No. 585,890

17 Claims. (Cl. 200149) This invention relates to improvements in moldedswitch heads of the type seen in Patent No. 2,287,676 to W. H. Frank etal. and Patent No. 2,302,849 to W. H.- Frank et al.

Switches of the above noted type in essence provide a first and secondstationary contact which are engaged and disengaged by a movable contactelement or slug. The contact slug is positioned within the switch headand the switch head is further constructed so as to move an insulatingbarrier between the stationary contacts as the contact slug is moved toa disengaged position. The head is further constructed so as tocompletely surround the area of contact engagement with an insulatingmeans. Hence, as the switch head is moved to a disengaged contactposition, arcing between the stationary contacts is decreased, firstbecause of the interposition of the insulating barrier and secondly,because the amount of oxygen or ionizable gas present is restricted inview of the insulated enclosure around the contact area.

In the past, it has been the practice to attach an operating clamp tothe top of the insulatnig material of the switch head, which operatingclamp provides the means whereby the switch head is moved between theengaged and disengaged positions. This practice, however, places a.tension strain on the material of the switch head, which is notnecessarily constructed to withstand this type of strain.

Furthermore, in the event of severe arcing it is possible that thisinsulating material would be damaged and there would then be no way inwhich the movable contact slug could be moved to a fully disengagedposition with respect to the stationary contacts.

Our novel invention avoids the two disadvantages inherent in thepresently used construction as above noted, by so constructing theoperating clamp and switch head so that the operating clamp will tend tocompress the material between the operating clamp and the contact slugwhen the switch head is moved to a disengaged position. In a preferredembodiment, this may be accom: plished by providing recesses in the sidewalls of the interior of the head casing within which the contact slugwill be positioned and to provide recesses in the external surface ofthe head casing, whereby an operating clamp formed in any desirablemanner as for example a spring wire may hook under a hollow protrusionin the said outer surface. In this construction, it is therefore seenthat the spring wire of the operating clamp will be positioned beneaththe protruding end of the slug which fits into the interior recesses ofthe head casing, and upon operation of this operating clamp to move theswitch head to a disengaged position, the operating clamp wire willcause the casing material between the operating clamp and the slugprojection to be in compression.

In view of this type construction, two advantages are immediatelyobtained. The first advantage is that the insulating material will beput into a compression strain during operation of the switch head andsecondly, in the event of destruction due to severe arcs of the switchice head insulation, it will still be possible for the operating clampto engage the contact slug at its protruding ends and move this contactslug to a fully disengaged position.

Accordingly, a primary object of our invention is to provide a switchhead construction wherein the insulated casing is put into a compressionstrain upon operation of the switch heads.

Another object of our invention is to provide a switch head wherein theoperating clamp may engage the contact slug to move this slug to adisengaged position even though the insulating casing may be destroyedor broken.

Another object of our invention is to provide a contact slug for switchheads which has protruding ends positioned to be engaged through aninsulating means by an operating clam-p.

Switching heads of the type to which our invention is directed, areusually provided with a spring biasing means for obtaining strongcontact engagement between the movable and stationary contacts. Hence,the essentials of a switching head would comprise the insulated casing,the contact slug, the insulating barrier, the spring biasing means andthe operating clamp. We have found that these components could beassembled in a novel manner which leads to the desirable features ofsimplicity, ease of manufacture, and long creepage distance between thecurrent carrying elements, and the operating clamp which might be at aground potential.

This novel construction comprises the features of making the insulatedbarrier an integral part of one half of the contact head insulatingcasing. The recesses above described in conjunction with the feature ofallowing the switch head insulation to be in compression, are thenfurther formed not only to side mount the contact slug, but to sidemount the contact biasing spring as well. After placing these componentsin their respective positions, the other half of the insulated casing,which has cooperating recesses for the contact slug and biasing springis then placed in a telescoping arrangement with the first half.

This second half is further formed to have a slot which will cooperatewith the insulating barrier, to thereby decrease distortion and warpageunder operating conditions.

Furthermore, the telescoping arrangement will provide a greatlyincreased creepage distance from the contact elements to the springclamp which is subsequently fastened to the insulated head in the mannerdescribed above, and in a further manner, so as to maintain twotelescoping connections in engagement with one another.

Another object of our invention is to provide a novel molded switch headconstruction which side mounts the components thereof, and physicallysecures these parts in a simplified manner.

Another object of our invention is to provide a molded switch head inwhich the insulating casing is formed of a first and second section,which are telescopically connected to one another and are held in theirclosed position by means of an operating clamp.

A still further object of our invention is to provide a molded switchhead constructed of two telescoping halves, whereby the creepagedistance between the contact structure and exterior parts of the switchhead are relatively large.

In the past, the entire surface of the insulating barrier which followsthe movable contact slug is in engagement with the entire surface of thefixed contact members or switch jaws.

A further object of our invention is to provide protrusions on thesurface of the insulating barrier, which will maintain a portion of thesurfaces of the switch jaws and insulating barrier at a predetermineddistance, so

that foreign matter which might result in short circuits and damage tomechanical operating parts of the switch head may be confined withinthis space.

These and other objects of our invention will become apparent when takenin conjunction with the drawings in' which: I

Figure l shows an exploded perspective view of our novel switch head.

Figure 2' shows a perspective view of one of the tele scoping insulatingcasing sections of Figure 1.

Figure 3 shows a cross-sectional 'view' of the switch head of Figure 1when assembled. v

Figure '4' shows a cross section view of Figure 3 when taken across thelines 4-4.

Figure 5 is similar to Figure 4 and shows the switch head in adisengaged position.

Figure 6 is a cross-sectional view of Figure 3 when taken across thelines 66.

Figure 7 is a side view of the assembled switch of Figure 1.

Figure 8 is a front exploded view of a second embodiment of ourinvention.

Figure 9 is a side view of Figure 8.

The exploded perspective view of Figure 1 clearly shows the fivecomponents of the switch head of our novel invention. These componentsare the first insulated casing section 20, a second insulated casingsection 21, a contact slug 22, biasing means 23 and the operating clamp24. Insulating section 21 is further shown in Figure 2, when seenlooking into the interior thereof. It is seen in both of Figures 1 and2, that the sections 21 and 22 are so molded to provide a ledge 25 and26 respectively on which the surfaces 27 and 28 of the movable contactslug 22 may be seated. Similarly, each of sections 20 and 21 areprovided with ledges such as 29 and 30 to seat portions 31 and 32 of thebiasing spring 23 of Figure 1. The ledges 25, 26, 29 and 30 may befurther seen in reference to Figure 3, which shows the relativepositions of contact slug 22 and spring 23 with respect to these ledges.

As then shown in each of Figures 1, 4 and 5, the insulated casingsection 20 contains the insulating barrier 33 as an integral portionthereof. This barrier 33 is provided with protrusions 34 and 35, whichas will be shown hereinafter, are effective to prevent dirt or foreignparticles from entering the contact area.

It is further seenwith reference to Figures 4 and 5, that the insulatingbarrier 33, in conjunction with the side surfaces 36- and 37, serves toposition and guide the switch head with respect to the switch jaws 38and 39 when moving the switch head to the on position of Figure 4. Inorder to achieve a more rigid construction and to allow resistance todistortion and warpage under operating conditions of the barrier 33, thesecond insu-l'ating. section 21,- which: has a protruding portion 40which may be telescopically insertedinto the first section 20, isfurther provided with a notch. 41, which when the sections 20 and 21 aretelescopically engaged, will receive aportion of the insulated barrier33.

As'now seen in Figures 1 and 3, the outer surface of sections 20 and 21is provided with: projecting abutments 42 and 43, which abutmentsinternally receive the protruding portions of slug 22 which form theledges 27 and 28. The operating clamp 24 of Figures 1 and 3, which mayhe formedof spring wire, includes a hook 44 and 45 at each side so as toengage the protruding abutments 42 and 43 in the manner shown in Figures3 and 7. The top portion 46 of the operating clamp 24 is then soconstructed as to be capable of receiving a .bar 47 which may be thecommon: operating. bar. for a plurality of switch heads.

Hence, the first feature of our novel switch head of 'simplicitpofmanufacture is now'apparent since one need only insert the contact slug22 and the spring biasing means 23 in their respective positions withrespect to the first section 20 and thereafter'bring the second section21 into its telescopic engagement with the first section 20. Theoperating clamp 24 is then brought into position as seen in Figures 3and 7, so that it will serve the dual function of an operating means anda means to maintain the assembly fixed.

Figures 3 and 7 specifically illustrate our novel feature ofconstructing the operating clamp and switch head in such a manner thatthe insulating material of the switch head will be put in compressionresponsive. to operation of the operating means, and furthermore thatalthough the insulating body of the switch head be destroyed, thatoperation of the operating means 24 will still be efiective to removethe contact slug 22. to a completely disengaged position with respect tothe stationary contact members 38 and 39.

That is to say, the operating clamp 24 of Figures 3 and 7 is shown asbeing positioned beneath the abutments 42 and 43 of section 20, whereprotrusions 27 and 28 of contact slug 22 project into the abutments 42and 43. Hence, if the switch head is to be moved to a disengaged or offposition, spring portions 44 and 45 will operate on the contact slugportions 27 and 28 through the insulating material of section 20, tothereby place this insulating material in compression.

When moving the switch to the engaged or on position, the bar or bale 47engages the top of member 20 and through surfaces 29 and 30 imparts aforce to the biasing means 23 and contact slug 22, to the on position ofFigure 4. Hence, in moving the switch head to the on position it is seenthat the entire assembly is put into compression strain.

Furthermore, if the insulating material of the switch head section 20 bedestroyed by severe arcing in the con.- tact area or breakage, it isseen that upon moving the operating member 24 to a disengaged positionthat portions 44 and 45 of the operating member 24 will come intophysical contact with projections 27 and 28 of the contact slug 22 tothereby move this contact slug 22 to a completely engaged position withrespect to the stationary contact 38 and 39.

Our novel switch head further provides a greater creepage distance fromthe contact area to the outer portions of the insulating body, such asthe operating, clamp 24 by virtue of our novel telescoping arrangement.This may be seen with reference to Figure 6, which specifically showsthe creepage distance as comprising a. path. across the surface ofprotusion 40 of the second insulatinghead section 21, and thereafter, tothe outermost portions of the switch head. It is to be noted, that inpast. arrangements, that the creepage due to telescoping. section wasnot provided and the creepage was merely that of one thickness of theinsulation.

The operation of our novel switch head may be. seen in conjunction withFigures 4 and 5, wherein. Figure-4 shows the contact slug 22 in itsengaged position. with respect to stationary conductors 38'and 39'.

When moving the contact engaged position, in. view of the enclosedconstruction around the area of contact disengagement, the amount ofoxygen or ionized gases entering the enclosure will be restricted sincethe internal pressure caused by these gases will be higher than theexternal pressure and arcs will rapidly extinguish.

' Figures 4 and. 5 show a further novel feature of our invention whichis based on the provision of the en.- larged sections 34 and 35 of thebarrier member 33. it is clearly seen in Figures 4 and 5, that theseenlargedsections provide spaces 50 and 51 between the surfaceof thebarrier 33' and the surface of conductors '38 and .39. These spaces 50and 51. are so positioned as to receive foreignmatter which wouldotherwise .act to gall, thecons tact surfaces of conductors '33 and '39and contact slug 22 or result in short circuits between the variousconductors. These spaces also allow for blistering or warping of barrier33 under excessive heat conditions which would otherwise fracture theinsulating material.

A second embodiment of this novel invention may be seen in the explodedfront and side views of Figures 8 and 9 respectively. The embodiments ofFigures 8 and 9 differs from that of the previous figure in that theinsulating barrier following the contact slug is an integral part of thecasing 61 while the contact slug 62 and biasing means 63 are sidemounted in the casing 61 at the top of the housing. Hence, surfaces 64and 65 of contact slug 62 are seated on ledges 66 and 67 of housing 61while surfaces 68 and 69 of spring 63 are positioned on ledges 70 and 71of housing 61.

The insertable head 72 is then connected in telescoping relationshipwith respect to the housing 61 so that when the unit is assembledsurface 73 of insert 72 will be flush with the upper surface of thehousing 61.

Fastened to the insert 72 is the plate 74 having the hook end 75 as anintegral portion thereof which may be utilized for moving the switchhead to a disengaged position.

A spring shaped clamp 76 is then connected to the plate 74 in anydesired manner and is positioned under the protruding hollow portions 77and 78 of the housing 61 when the insert 72 is in its closed telescopingrelation with respect to the housing 61.

Hence, it is seen that in the case of Figures 8 and 9 as well as in thepreceding figures, that when the switch head is moved to a disengagedposition, the clamp 76 will place the material between it and thecontact slug 62 in compression. Similarly, the embodiment of Figures 8and 9 present the advantages of side mounting and the telescopingengagement between the two portions of the switch head housing.

In the foregoing, we have described our invention solely in connectionwith specific illustrative embodiments thereof. Since many variationsand modifications of the invention will now be obvious to those skilledin the art, we prefer to be bound not by the specific disclosure hereincontained but only by the appended claims.

We claim:

1. A switch head having an operating means for moving a contact sluginto and out of engagement with a first and second stationary conductor;said switch head comprising a first and second insulating head section;a biasing means and a contact slug; said first insulating head sectionhaving depressions therein for receiving and positioning one end of saidcontact slug and biasing means; said second insulating head sectionbeing connectible to said first insulating head section; said secondinsulating head section having depressions therein for receiving andpositioning the other end of said contact slug and biasing means whensaid first and second insulating head sections are connected; saidbiasing means being positioned to move stationary conductors intoengagement with said contact slug when said switch head is moved to theengaged position; said operating means being connected to said switchhead adjacent said depressions to place the portion of said switch headbetween said operating means and said contact slug in compression whensaid operating means moves said contact slug out of engagement with saidfirst and second stationary conductors.

2. A switch head having an operating means for moving a contact sluginto and out of engagement with a first and second stationary conductor;said switch head comprising a first and second insulating head sectionand a contact slug; said first insulating head section havingdepressions therein for receiving and positioning one end of saidcontact slug; said second insulating head section being connectible tosaid first insulating head section; said second insulating head sectionhaving depressions therein for receiving and positioning the other endof said contact slug when said first and second insulating head sectionsare connected; said operating means being connected to said switch headadjacent said depressions to place the portion of said switch headbetween said' operating means and said contact sing in compression whensaid operating means moves said contact slug out of engagement with saidfirst and second stationary conductors.

3. A switch head for moving a contact slug into and out of engagementwith a first and second stationary conductor; said switch headcomprising a first and second insulating head section; an operatingspring clamp, and a contact slug; said first insulating head sectionhaving depressions therein for receiving and positioning one end of saidcontact slug; said second insulating head section having depressionstherein for receiving and positioning the other end of said contact slugwhen said first and second insulating head sections are connected; saidoperating spring clamp being constructed to move said switch head intoand out of engagement; said operating spring clamp being connected tosaid switch head adjacent said depressions to thereby place the portionof said switch head between said operating spring clamp and said contactslug in compression when said operating spring clamp moves said contactslug'out of engagement with said first and second stationary conductor;said operating spring clamp being further constructed to maintain saidfirst and second insulating head sections connected to one another.

4. A switch head having an operating means for moving a contact sluginto and out of engagement with a first and second stationary conductor;said switch head comprising a first and second insulating head sectionand a contact slug; said first insulating head section havingdepressions therein for receiving and positioning one end of saidcontact slug; said second insulating head section being connectible tosaid first insulating head section; said second insulating head sectionhaving depressions therein for receiving and positioning the other endof said contact slug when said first and second insulating head sectionsare connected in telescoping relationship with respect to one another;said operating means being connected to said switch head adjacent saiddepressions to place the portion of said switch head between saidoperating means and said contact slug in compression when said operatingmeans moves said contact slug out of engagement with said first andsecond stationary conductors.

5. A switch head having an operating means for moving a contact sluginto and out of engagement with a first and second stationary conductor;said switch head comprising a first and second insulating head section,an insulating barrier and a contact slug; said first insulating headsection having depressions therein for receiving and positioning saidcontact slug; said second insulating head section being connectible tosaid first insulating head section; said insulating barrier beingconstructed to follow said contact slug when said contact slug is movedto a disengaged position; said insulating barrier being an integralportion of said first insulating head section; said second insulatinghead section being constructed to have .a depression therein forreceiving a portion of said insulating barrier when said first andsecond head sections are connected to one another; said'operating meansbeing connected to said switch head adjacent said depressions to placethe portion of said switch head between said operating means and saidcontact slug in compression when said operating means moves said contactslug out of engagement with said first and second stationary conductors.

6. A switch head having an operating means for mov ing a contact sluginto and out of engagement with a first and second stationary conductor;said switch head comprising a first and second insulating head section,an insulating barrier and a contact slug; said first insulating headsection having depressions therein for receiving and positioning saidcontact slug; said second insulating head section being connectible intelescoping relationship to:.saidtfirst insulating head section; saidinsulating barrier beingconstructed to. follow said contact slug whensaid contact: slug is moved to a disengagedposition; said insulatingbarrier being an integral portion of said first insulating head section;said second insulating head section being constructed to have adepression therein for receiving a portion of said insulatingbarrierwhensaid first and second head sections are connected to oneanother;said operating means being connected to said switch head adjacent saiddepressions to place the POI:- tionof said switch head between saidoperating'means and said contact slug in compression when said operatingmeans .moves said contact slug out of engagement with said .first and.second stationary conductors.

7. A switch head having an operating spring clamp for moving a contactslug into and out of engagement with a first and second stationaryconductor; said switch head comprising a first and second insulatinghead section and a contact slug; said first and second insulating headsections being connectible in-telescoping relationship to one another;said contact slug being mountedwithinsaid first and second insulatinghead section; said first and second insulating head sections beingconstructed to allow access of said contact slug to stationary contactmembers, said operating spring clamp being operatively connected tosaid. switch head to place theportion of said switch head between saidoperating spring clamp and said contact slug in compression when saidoperating spring clamp moves said contact slug out. of engagementwithsaid first and secondstationary conductor.

8. A switch head for moving a contact slug intoand out of engagementwith a first and second stationary conductor; said switch headcomprising a first and second insulating head section, an operatingspringclamp and acontact slug; said first and second insulating headsections being connectible to one another; said contact slugv beingmounted within said first and second insulating head section; said firstand second insulating head sec tions being constructed to allow accessof said contact slug-to stationary contact members; said operatingspring clamp being. constructed to. move said switch head into and outof engagement; said operating spring clamp being operativelyconnectedto. said switch head to place the portion of said switch head betweensaid operating spring clamp. and said contact slug in compression whensaid operating. spring. clamp moves said contact slug out of engagementwith said first and second stationary conductor; said operating springclamp being further constructed to maintain said first and secondinsulating head sections connected to one another.

7 9. A. switch head for moving a. contact slug into and out ofengagement with a first and second stationary conductor; said switchhead comprising a first and second insulating head section, an operatingspring clamp and. a: contact slug; said first and second insulating headsections being. connectible in telescoping relationship to one another;said contact slug being mounted within said first and second insulatinghead section; said first and secondinsulating head sections. beingconstructed to allow access of said contact. slug to: stationary contactmembers; said operating spring clamp being constructed to move saidswitch head into and out of engagement; said operating spring clampbeing operatively connected to said switch head to place the portion ofsaid switch head between said operating spring clamp and said contactsing in compression when said operating spring clamp moves said contactslug out of engagement with said first and second stationary conductor;said operating spring clamp being further constructed to maintain saidfirst and second insulating head sections connected toone another.

101 A switch head 'for moving a contact slug intov and out. 'ofiengagement with a first and second stationary conductor; said? switchhead comprising an insulating casing, an operating; means and a. contactslug; said contact slug being mounted within said insulated casing;

8 saidxinsulated casing being constructed to allow said contact slugaccess. to cooperating stationary conductors; said insulating. casinghaving anexternal protrusion; a portionof'saidcontact sing beingpositioned within said external protrusion;.saidoperating means beingconnected to said protrusion to, place the material of said insulatingcasing betweensaid operating means andsaid portion of said. contact slugin compression when said operating meansmoves. said switch head to adisengaged position.

ll. .A-tswitch head for moving a contact slug into and out of engagementwith a firstandsecond stationary conductorasaid switchvhead comprisingan-insulating casing, an operating means and a contact slug; saidcontact slug being mounted within said insulated: casing; saidinsulated: casing being constructed to allow said contact slug accesstocooperatingsta-tionary conductors; said insulating casing having-anexternal protrusion; a portion of said contact slug; being positionedwithin said external protrusiomsa-idioperating-meansbeing connected tosaid protrusion-to place the materialof said insulating casing betweensaidwoperating means and said portion of said contact: slugincompression when said operating means moves. said switch head to adisengaged position; said operating-means; being engageable with said.portion of said contact slug in the absenceof said insulating materialbetween saidtoperating means and saidcontact slug portion.

12. Aswitchhead'for moving a contact slug into and out of, engagementwith a first and second stationary conductor; said switchzheadcomprisingan insulating casing, an operatingspring clamp andia contact slug; saidconitactxslug being mounted within said insulating casing; saidinsulating casing being constructed to allow said contact slugaccesstolcooperating stationary conductors;

said insulating; casing having. a: first andisecond external protrusion;a first. and second portion of said contact slug' being positioned.within said first and second protrusions respectively; said operatingspring clamp being operatively connected to said first and secondprotrusions to place the material of said insulating casing between saidcontact slug. and; said. operating spring clamp in compression when saidoperating, spring clamp moves said switch head toua disengaged position.

13. A switchtlreadfor-moving acontact slug into and out ofengagementwitlr a first and'second stationary conductor; said switchhead. comprising an insulating casing, an operating spring clamp and a.contact slug; said contact slug being mounted Wlii'llfi said insulatingcasing; said insulating-casing: having a first and second externalprotrusion; a first andseccnd. portion of said contact slug being.positionediwithin said first and second protrusionsrespectively;said2operatingspring clamp being operatively connected tosaid first and second protrusions to place the material. of saidinsulating. casing between said contact slug. and said, operating springclamp in compression when said operating spring clamp moves said switchhead to a disengaged positiomsaid. insulating casing comprising a firstandsecond: section connected in telescoping relationship;.saidoperatingspring clamp being further constructed to maintain said firstand second sections in their sai-dtelescoping relationship.

14. A switch head for movinga, contact slug into and out of engagementwith: a first and second stationary conductor; said switch headcomprising a first and second insulating head section and a contactslug; said first insulating head section having depressions therein forreceiving and positioning one end of said contact slug; said secondinsulating head section being connectible to said first insulating headsection; said second insulating head section having depressions thereinfor receiving and positioning the other end of said contact slug whensaid first and second insulating head sections are connected; said.first and second insulating head sections having a first and secondvprotrusion respectively; a first and second portion of said contact slugbeing positioned within said first and second protrusions respectively;an operating spring clamp; said operating spring clamp being operativelyconnected to said first and second protrusions to place the material ofsaid insulating casing between said contact slug and said operatingspring clamp in compression when said operating spring clamp moves saidswitch head to a disengaged position.

15. A switch head for moving a contact slug into and out of engagementwith a first and sec-ond stationary conductor; said switch headcomprising a first and second insulating head section and a contactslug; said first insulating head section having depressions therein forreceiving and positioning one end of said contact slug; said secondinsulating head section being connectible to said first insulating headsection; said second insulating head section having depressions thereinfor receiving and positioning the other end of said contact slug whensaid first and second insulating head sections are connected; said firstand second insulating head sections having a first and second protrusionrespectively; a first and second portion of said contact slug beingpositioned within said first and second protrusions respectively; anoperating spring clamp; said operating spring clamp being operativelyconnected to said first and second protrusions to place the material ofsaid insulating casing between said contact slug and said operatingspring clamp in compression when said operating spring clamp moves saidswitch head to a disengaged position; said operating spring clamp beingconstructed to move said switch head into and out of engagement; saidoperating spring clamp being further constructed to maintain said firstand second insulating head sections connected to one another.

16. A switch head for moving a contact slug into and out of engagementwith a first and second conductor; said switch head comprising aninsulating .casing having a contact slug and an insulating barriermounted therein; said insulating barrier being positioned with respectto said contact slug to follow said contact slug when said contact slugis moved to a disengaged position; said insulating barrier having afirst surface adjacent to the area to be filled by said first conductorand a second surface adjacent to the area to be filled by said secondconductor; said first and second surfaces of said insulating barrierhaving depressions therein to provide spacing of at least a portion ofsaid first and second surface of said insulating barrier and at least aportion of conductors moved into said area to be filled by first andsecond conductors; said contact slug being moved into and out ofengagement with said first and second conductors without said first andsecond conductors entering said spacing.

17. A switch head for moving a contact slug into and out of engagementwith a first and second stationary conductor; said switch headcomprising a first and second insulating head section, an insulatingbarrier and a contact slug; said first insulating head section havingdepressions therein for receiving and positioning said contact slug;said second insulating head being connectible to said first insulatinghead section; said insulating barrier being constructed to follow saidcontact slug when said contact slug is moved to a disengaged position;said insulating barrier being an integral portion of said firstinsulating head section; said second insulating head section beingconstructed to have a depression therein for receiving a portion of saidinsulating barrier when said first and second head sections areconnected to one another; said insulating barrier having a first surfaceadjacent to the area to be filled by said first conductor and a secondsurface adjacent to the area to be filled by said second conductor; saidfirst and second surfaces of said insulating barrier having depressionstherein to provide spacing of at least a portion of said first andsecond surface of said insulating barrier and at least a portion ofconductors moved into said area to be filled by first and secondconductors; said contact slug being moved into and out of engagementwith said first and second conductors without said first and secondconductors entering said spacing.

References Cited in the file of this patent UNITED STATES PATENTS1,951,297 Von Norman Mar. 13, 1934 2,130,589 Lantz Sept. 20, 19382,230,428 Frank Feb. 4, 1941 2,287,676 Frank et a1. June 23, 19422,393,385 Lankmeier Jan. 22, 1946 2,561,450 Russell July 24, 1951

